why result is zero?

5 Ansichten (letzte 30 Tage)
Habib
Habib am 10 Mär. 2015
Kommentiert: Torsten am 10 Mär. 2015
Hi everybody. In second "for" nesting loop, I want to use Trapz command (numerical integration) for integration from an N*N matrix (u_2) but I got zero answer? What is wrong? I hope one give an answer.
clc
clear all
close all
aa=3e-2;
E0=10000;
z=0.42;
L=z;
N=100;
lambda=1030e-9;
k=2*pi/lambda;
w0=0.0001;
zr=pi*w0^2/lambda;
R=z*(1+(zr/z)^2);
w=w0*sqrt(1+(z/zr)^2);
D1=linspace(-aa/2,aa/2,N);
[x,y]=meshgrid(D1,D1);
b=(lambda*L)/(N*aa);
D2=linspace(-b/2,b/2,N);
[xx,yy]=meshgrid(D2,D2);
RR=1.5;
u1=ones(size(x));
u_2=u1;
u2=ones(size(xx));
[teta,r]=cart2pol(x,y);
[teta1,rr] = cart2pol(xx,yy);
for i=1:N
for j=1:N
u1(i,j)=E0*(r(i,j)/w)*exp(-(r(i,j)/w).^2);
end
end
for i=1:N
for j=1:N
u_2(i,j)=u1(i,j)*besselj(1,-k*r(i,j)*rr(i,j))*exp(-1i*k*rr(i,j)^2/(L*w^2))*cos(teta1(i,j));
u2(i,j)=trapz(u_2(i,j));
end
end
  2 Kommentare
Habib
Habib am 10 Mär. 2015
Thank you for your answer.
I read it, but i couldn't understand what is wrong. Now, what must I do? how i can fixed it?
Torsten
Torsten am 10 Mär. 2015
x = -3:.1:3;
y = -5:.1:5;
[X,Y] = meshgrid(x,y);
F = X.^2 + Y.^2;
I = trapz(y,trapz(x,F,2));
integrates the function f(x,y)=x^2+y^2 over the rectangle [-3:3]x[-5:5].
Now insert your function and your domain of integration.
Best wishes
Torsten.

Melden Sie sich an, um zu kommentieren.

Melden Sie sich an, um diese Frage zu beantworten.

Akzeptierte Antwort

Torsten
Torsten am 10 Mär. 2015
Take a look at the chapter "Multiple numerical integrations" under
http://de.mathworks.com/help/matlab/ref/trapz.html
to see what is wrong with your call to trapz.
Best wishes
Torsten.

Weitere Antworten (0)

Kategorien

Mehr zu Numerical Integration and Differentiation finden Sie in Help Center und File Exchange

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by